The nature of the inflammatory and suppurative processes will be considered in detail later; suffice it here to say that they are brought about by the action of one or other of the organisms that we have now to consider.
It is found that the _staphylococci_, which cl.u.s.ter into groups, tend to produce localised lesions; while the chain-forms--_streptococci_--give rise to diffuse, spreading conditions. Many varieties of pyogenic bacteria have now been differentiated, the best known being the staphylococcus aureus, the streptococcus, and the bacillus coli communis.
[Ill.u.s.tration: FIG. 2.--Staphylococcus aureus in Pus from case of Osteomyelitis. 1000 diam. Gram"s stain.]
_Staphylococcus Aureus._--This is the commonest organism found in localised inflammatory and suppurative conditions. It varies greatly in its virulence, and is found in such widely different conditions as skin pustules, boils, carbuncles, and some acute inflammations of bone. As seen by the microscope it occurs in grape-like cl.u.s.ters, fission of the individual cells taking place irregularly (Fig. 2). When grown in artificial media, the colonies a.s.sume an orange-yellow colour--hence the name _aureus_. It is of high vitality and resists more prolonged exposure to high temperatures than most non-sporing bacteria. It is capable of lying latent in the tissues for long periods, for example, in the marrow of long bones, and of again becoming active and causing a fresh outbreak of suppuration. This organism is widely distributed: it is found on the skin, in the mouth, and in other situations in the body, and as it is present in the dust of the air and on all objects upon which dust has settled, it is a continual source of infection unless means are taken to exclude it from wounds.
The _staphylococcus albus_ is much less common than the aureus, but has the same properties and characters, save that its growth on artificial media a.s.sumes a white colour. It is the common cause of st.i.tch abscesses, the skin being its normal habitat.
[Ill.u.s.tration: FIG. 3.--Streptococci in Pus from an acute abscess in subcutaneous tissue. 1000 diam. Gram"s stain.]
_Streptococcus Pyogenes._--This organism also varies greatly in its virulence; in some instances--for example in erysipelas--it causes a sharp attack of acute spreading inflammation, which soon subsides without showing any tendency to end in suppuration; under other conditions it gives rise to a generalised infection which rapidly proves fatal. The streptococcus has less capacity of liquefying the tissues than the staphylococcus, so that pus formation takes place more slowly.
At the same time its products are very potent in destroying the tissues in their vicinity, and so interfering with the exudation of leucocytes which would otherwise exercise their protective influence. Streptococci invade the lymph s.p.a.ces, and are a.s.sociated with acute spreading conditions such as phlegmonous or erysipelatous inflammations and suppurations, lymphangitis and suppuration in lymph glands, and inflammation of serous and synovial membranes, also with a form of pneumonia which is p.r.o.ne to follow on severe operations in the mouth and throat. Streptococci are also concerned in the production of spreading gangrene and pyaemia.
Division takes place in one axis, so that chains of varying length are formed (Fig. 3). It is less easily cultivated by artificial media than the staphylococcus; it forms a whitish growth.
[Ill.u.s.tration: FIG. 4.--Bacillus coli communis in Urine, from a case of Cyst.i.tis. 1000 diam. Leishman"s stain.]
_Bacillus Coli Communis._--This organism, which is a normal inhabitant of the intestinal tract, shows a great tendency to invade any organ or tissue whose vitality is lowered. It is causatively a.s.sociated with such conditions as peritonitis and peritoneal suppuration resulting from strangulated hernia, appendicitis, or perforation in any part of the alimentary ca.n.a.l. In cyst.i.tis, pyelitis, abscess of the kidney, suppuration in the bile-ducts or liver, and in many other abdominal conditions, it plays a most important part. The discharge from wounds infected by this organism has usually a ftid, or even a faecal odour, and often contains gases resulting from putrefaction.
It is a small rod-shaped organism with short flagellae, which render it motile (Fig. 4). It closely resembles the typhoid bacillus, but is distinguished from it by its behaviour in artificial culture media.
[Ill.u.s.tration: FIG. 5.--Fraenkel"s Pneumococci in Pus from Empyema following Pneumonia. 100 diam. Stained with Muir"s capsule stain.]
_Pneumo-bacteria._--Two forms of organism a.s.sociated with pneumonia--_Fraenkel"s pneumococcus_ (one of the diplococci) (Fig. 5) and _Friedlander"s pneumo-bacillus_ (a short rod-shaped form)--are frequently met with in inflammations of the serous and synovial membranes, in suppuration in the liver, and in various other inflammatory and suppurative conditions.
_Bacillus Typhosus._--This organism has been found in pure culture in suppurative conditions of bone, of cellular tissue, and of internal organs, especially during convalescence from typhoid fever. Like the staphylococcus, it is capable of lying latent in the tissues for long periods.
_Other Pyogenic Bacteria._--It is not necessary to do more than name some of the other organisms that are known to be pyogenic, such as the bacillus pyocyaneus, which is found in green and blue pus, the micrococcus tetragenus, the gonococcus, actinomyces, the glanders bacillus, and the tubercle bacillus. Most of these will receive further mention in connection with the diseases to which they give rise.
#Leucocytosis.#--Most bacterial diseases, as well as certain other pathological conditions, are a.s.sociated with an increase in the number of leucocytes in the blood throughout the circulatory system. This condition of the blood, which is known as _leucocytosis_, is believed to be due to an excessive output and rapid formation of leucocytes by the bone marrow, and it probably has as its object the arrest and destruction of the invading organisms or toxins. To increase the resisting power of the system to pathogenic organisms, an artificial leucocytosis may be induced by subcutaneous injection of a solution of nucleinate of soda (16 minims of a 5 per cent. solution).
The _normal_ number of leucocytes per cubic millimetre varies in different individuals, and in the same individual under different conditions, from 5000 to 10,000: 7500 is a normal average, and anything above 12,000 is considered abnormal. When leucocytosis is present, the number may range from 12,000 to 30,000 or even higher; 40,000 is looked upon as a high degree of leucocytosis. According to Ehrlich, the following may be taken as the standard proportion of the various forms of leucocytes in normal blood: polynuclear neutrophile leucocytes, 70 to 72 per cent.; lymphocytes, 22 to 25 per cent.; eosinophile cells, 2 to 4 per cent.; large mononuclear and transitional leucocytes, 2 to 4 per cent.; mast-cells, 0.5 to 2 per cent.
In estimating the clinical importance of a leucocytosis, it is not sufficient merely to count the aggregate number of leucocytes present. A differential count must be made to determine which variety of cells is in excess. In the majority of surgical affections it is chiefly the granular polymorpho-nuclear neutrophile leucocytes that are in excess (_ordinary leucocytosis_). In some cases, and particularly in parasitic diseases such as trichiniasis and hydatid disease, the eosinophile leucocytes also show a proportionate increase (_eosinophilia_). The term _lymphocytosis_ is applied when there is an increase in the number of circulating lymphocytes, as occurs, for example, in lymphatic leucaemia, and in certain cases of syphilis.
Leucocytosis is met with in nearly all acute infective diseases, and in acute pyogenic inflammatory affections, particularly in those attended with suppuration. In exceptionally acute septic conditions the extreme virulence of the toxins may prevent the leucocytes reacting, and leucocytosis may be absent. The absence of leucocytosis in a disease in which it is usually present is therefore to be looked upon as a grave omen, particularly when the general symptoms are severe. In some cases of malignant disease the number of leucocytes is increased to 15,000 or 20,000. A few hours after a severe haemorrhage also there is usually a leucocytosis of from 15,000 to 30,000, which lasts for three or four days (Lyon). In cases of haemorrhage the leucocytosis is increased by infusion of fluids into the circulation. After all operations there is at least a transient leucocytosis (_post-operative leucocytosis_) (F. I. Dawson).
The leucocytosis begins soon after the infection manifests itself--for example, by shivering, rigor, or rise of temperature. The number of leucocytes rises somewhat rapidly, increases while the condition is progressing, and remains high during the febrile period, but there is no constant correspondence between the number of leucocytes and the height of the temperature. The arrest of the inflammation and its resolution are accompanied by a fall in the number of leucocytes, while the occurrence of suppuration is attended with a further increase in their number.
In interpreting the "blood count," it is to be kept in mind that a _physiological leucocytosis_ occurs within three or four hours of taking a meal, especially one rich in proteins, from 1500 to 2000 being added to the normal number. In this _digestion leucocytosis_ the increase is chiefly in the polynuclear neutrophile leucocytes. Immediately before and after delivery, particularly in primiparae, there is usually a moderate degree of leucocytosis. If the labour is normal and the puerperium uncomplicated, the number of leucocytes regains the normal in about a week. Lactation has no appreciable effect on the number of leucocytes. In new-born infants the leucocyte count is abnormally high, ranging from 15,000 to 20,000. In children under one year of age, the normal average is from 10,000 to 20,000.
_Absence of Leucocytosis--Leucopenia._--In certain infective diseases the number of leucocytes in the circulating blood is abnormally low--3000 or 4000--and this condition is known as _leucopenia_. It occurs in typhoid fever, especially in the later stages of the disease, in tuberculous lesions unaccompanied by suppuration, in malaria, and in most cases of uncomplicated influenza. The occurrence of leucocytosis in any of these conditions is to be looked upon as an indication that a mixed infection has taken place, and that some suppurative process is present.
The absence of leucocytosis in some cases of virulent septic poisoning has already been referred to.
It will be evident that too much reliance must not be placed upon a single observation, particularly in emergency cases. Whenever possible, a series of observations should be made, the blood being examined about four hours after meals, and about the same hour each day.
The clinical significance of the blood count in individual diseases will be further referred to.
_The Iodine or Glycogen Reaction._--The leucocyte count may be supplemented by staining films of the blood with a watery solution of iodine and pota.s.sium iodide. In all advancing purulent conditions, in septic poisonings, in pneumonia, and in cancerous growths a.s.sociated with ulceration, a certain number of the polynuclear leucocytes are stained a brown or reddish-brown colour, due to the action of the iodine on some substance in the cells of the nature of glycogen. This reaction is absent in serous effusions, in unmixed tuberculous infections, in uncomplicated typhoid fever, and in the early stages of cancerous growths.
CHAPTER III
INFLAMMATION
Definition--Nature of inflammation from surgical point of view--Sequence of changes in bacterial inflammation--Clinical aspects of inflammation--General principles of treatment--Chronic inflammation.
Inflammation may be defined as the series of vital changes that occurs in the tissues in response to irritation. These changes represent the reaction of the tissue elements to the irritant, and const.i.tute the attempt made by nature to arrest or to limit its injurious effects, and to repair the damage done by it.
The phenomena which characterise the inflammatory reaction can be induced by any form of irritation--such, for example, as mechanical injury, the application of heat or of chemical substances, or the action of pathogenic bacteria and their toxins--and they are essentially similar in kind whatever the irritant may be. The extent to which the process may go, however, and its effects on the part implicated and on the system as a whole, vary with different irritants and with the intensity and duration of their action. A mechanical, a thermal, or a chemical irritant, acting alone, induces a degree of reaction directly proportionate to its physical properties, and so long as it does not completely destroy the vitality of the part involved, the changes in the tissues are chiefly directed towards repairing the damage done to the part, and the inflammatory reaction is not only compatible with the occurrence of ideal repair, but may be looked upon as an integral step in the reparative process.
The irritation caused by infection with bacteria, on the other hand, is c.u.mulative, as the organisms not only multiply in the tissues, but in addition produce chemical poisons (toxins) which aggravate the irritative effects. The resulting reaction is correspondingly progressive, and has as its primary object the expulsion of the irritant and the limitation of its action. If the natural protective effort is successful, the resulting tissue changes subserve the process of repair, but if the bacteria gain the upper hand in the struggle, the inflammatory reaction becomes more intense, certain of the tissue elements succ.u.mb, and the process for the time being is a destructive one. During the stage of bacterial inflammation, reparative processes are in abeyance, and it is only after the inflammation has been allayed, either by natural means or by the aid of the surgeon, that repair takes place.
In applying the antiseptic principle to the treatment of wounds, our main object is to exclude or to eliminate the bacterial factor, and so to prevent the inflammatory reaction going beyond the stage in which it is protective, and just in proportion as we succeed in attaining this object, do we favour the occurrence of ideal repair.
#Sequence of Changes in Bacterial Inflammation.#--As the form of inflammation with which we are most concerned is that due to the action of bacteria, in describing the process by which the protective influence of the inflammatory reaction is brought into play, we shall a.s.sume the presence of a bacterial irritant.
The introduction of a colony of micro-organisms is quickly followed by an acc.u.mulation of wandering cells, and proliferation of connective-tissue cells in the tissues at the site of infection. The various cells are attracted to the bacteria by a peculiar chemical or biological power known as _chemotaxis_, which seems to result from variations in the surface tension of different varieties of cells, probably caused by some substance produced by the micro-organisms.
Changes in the blood vessels then ensue, the arteries becoming dilated and the rate of the current in them being for a time increased--_active hyperaemia_. Soon, however, the rate of the blood flow becomes slower than normal, and in course of time the current may cease (_stasis_), and the blood in the vessels may even coagulate (_thrombosis_). Coincidently with these changes in the vessels, the leucocytes in the blood of the inflamed part rapidly increase in number, and they become viscous and adhere to the vessel wall, where they may acc.u.mulate in large numbers.
In course of time the leucocytes pa.s.s through the vessel wall--_emigration of leucocytes_--and move towards the seat of infection, giving rise to a marked degree of _local leucocytosis_.
Through the openings by which the leucocytes have escaped from the vessels, red corpuscles may be pa.s.sively extruded--_diapedesis of red corpuscles_. These processes are accompanied by changes in the endothelium of the vessel walls, which result in an increased formation of lymph, which transudes into the meshes of the connective tissue giving rise to an _inflammatory dema_, or, if the inflammation is on a free surface, forming an _inflammatory exudate_. The quant.i.ty and characters of this exudate vary in different parts of the body, and according to the nature, virulence, and location of the organisms causing the inflammation. Thus it may be _serous_, as in some forms of synovitis; _sero-fibrinous_, as in certain varieties of peritonitis, the fibrin tending to limit the spread of the inflammation by forming adhesions; _croupous_, when it coagulates on a free surface and forms a false membrane, as in diphtheria; _haemorrhagic_ when mixed with blood; or _purulent_, when suppuration has occurred. The protective effects of the inflammatory reaction depend for the most part upon the transudation of lymph and the emigration of leucocytes. The lymph contains the opsonins which act on the bacteria and render them less able to resist the attack of the phagocytes, as well as the various protective antibodies which neutralise the toxins. The polymorph leucocytes are the princ.i.p.al agents in the process of phagocytosis (p. 22), and together with the other forms of phagocytes they ingest and destroy the bacteria.
If the attempt to repel the invading organisms is successful, the irritant effects are overcome, the inflammation is arrested, and _resolution_ is said to take place.
Certain of the vascular and cellular changes are now utilised to restore the condition to the normal, and _repair_ ensues after the manner already described. In certain situations, notably in tendon sheaths, in the cavities of joints, and in the interior of serous cavities, for example the pleura and peritoneum, the restoration to the normal is not perfect, adhesions forming between the opposing surfaces.
If, however, the reaction induced by the infection is insufficient to check the growth and spread of the organisms, or to inhibit their toxin production, local necrosis of tissue may take place, either in the form of suppuration or of gangrene, or the toxins absorbed into the circulation may produce blood-poisoning, which may even prove fatal.
#Clinical Aspects of Inflammation.#--It must clearly be understood that inflammation is not to be looked upon as a disease in itself, but rather as an evidence of some infective process going on in the tissues in which it occurs, and of an effort on the part of these tissues to overcome the invading organisms and their products. The chief danger to the patient lies, not in the reactive changes that const.i.tute the inflammatory process, but in the fact that he is liable to be poisoned by the toxins of the bacteria at work in the inflamed area.
Since the days of Celsus (first century A.D.), heat, redness, swelling, and pain have been recognised as cardinal signs of inflammation, and to these may be added, interference with function in the inflamed part, and general const.i.tutional disturbance. Variations in these signs and symptoms depend upon the acuteness of the condition, the nature of the causative organism and of the tissue attacked, the situation of the part in relation to the surface, and other factors.
The _heat_ of the inflamed part is to be attributed to the increased quant.i.ty of blood present in it, and the more superficial the affected area the more readily is the local increase of temperature detected by the hand. This clinical point is best tested by placing the palm of the hand and fingers for a few seconds alternately over an uninflamed and an inflamed area, otherwise under similar conditions as to coverings and exposure. In this way even slight differences may be recognised.
_Redness_, similarly, is due to the increased afflux of blood to the inflamed part. The shade of colour varies with the stage of the inflammation, being lighter and brighter in the early, hyperaemic stages, and darker and duskier when the blood flow is slowed or when stasis has occurred and the oxygenation of the blood is defective. In the thrombotic stage the part may a.s.sume a purplish hue.
The _swelling_ is partly due to the increased amount of blood in the affected part and to the acc.u.mulation of leucocytes and proliferated tissue cells, but chiefly to the exudate in the connective tissue--_inflammatory dema_. The more open the structure of the tissue of the part, the greater is the amount of swelling--witness the marked degree of dema that occurs in such parts as the s.c.r.o.t.u.m or the eyelids.
_Pain_ is a symptom seldom absent in inflammation. _Tenderness_--that is, pain elicited on pressure--is one of the most valuable diagnostic signs we possess, and is often present before pain is experienced by the patient. That the area of tenderness corresponds to the area of inflammation is almost an axiom of surgery. Pain and tenderness are due to the irritation of nerve filaments of the part, rendered all the more sensitive by the abnormal conditions of their blood supply. In inflammatory conditions of internal organs, for example the abdominal viscera, the pain is frequently referred to other parts, usually to an area supplied by branches from the same segment of the cord as that supplying the inflamed part.
For purposes of diagnosis, attention should be paid to the terms in which the patient describes his pain. For example, the pain caused by an inflammation of the skin is usually described as of a _burning_ or _itching_ character; that of inflammation in dense tissues like periosteum or bone, or in encapsuled organs, as _dull_, _boring_, or _aching_. When inflammation is pa.s.sing on to suppuration the pain a.s.sumes a _throbbing_ character, and as the pus reaches the surface, or "points," as it is called, sharp, _darting_, or _lancinating_ pains are experienced. Inflammation involving a nerve-trunk may cause a _boring_ or a _tingling_ pain; while the implication of a serous membrane such as the pleura or peritoneum gives rise to a pain of a sharp, _stabbing_ character.
_Interference with the function_ of the inflamed part is always present to a greater or less extent.